Honestly I would get a check up at the dr’s office just to make sure. If its just one finger exhibiting the condition there could be an underlying problem.
As far as Beginners go I would steer riders away from them until you know you have full control and trunk (mid body) strength. Have that on the throttle and not see a sudden dip or rise in the road can become dangerous quick if your body and arms aren’t in a condition to remain somewhat un effected.
A 90 minute ride… I wouldn’t need it that short of a ride… though I am about to partake on a 500 mile jaunt (1,000 round trip) and thinking about it. I turn wrenches for a living though and forearm strength and control is not an issue with me.
Seriously even if it helped you on the short runs, it’s just a band aid covering up a potential problem.